Process for the production of shaped bodies from polyolefins

Abstract

The invention provides a process for the production of shaped bodies and semi-finished products from polyolefins in the presence of crosslink-reinforcing coagents by addition of 0.01 to 1.0 wt % of at least one organic polymer-active radical forming agent, and brief heating with shaping before radiation to above the decomposition temperature of the radical forming agent until the radical forming agent decomposes. The process serves for the production of pipes, shaped sections and sheaths by extrusion, injection molding or extrusion pressing, especially for electric insulations, in particular for cables and lines.

What is claimed is: 
     
       1. A process for the production of shaped bodies and semi-finished products from olefin homopolymers and copolymers crosslinkable by high energy radiation in the presence of a polyfunctional ethylenically unsaturated monomer capable of reducing the radiation dosage for cross-linking said olefin polymer comprising: a. forming a mixture of said olefin polymer, monomer and from 0.05 to 0.5% based on the weight of the said olefin polymer of at least one heat decomposable organic polymer active radical forming agent;   b. shaping said mixture and heating said mixture during or after shaping at a temperature above the decomposition temperature of said radical forming agent until said agent decomposes and a shaped crosslinkable body is formed whereby oligomerization of said monomer occurs so as to substantially prevent migration of said monomer to the surface of said shaped body; and   c. crosslinking said shaped body with high energy radiation.   
     
     
       2. The process of claim 1 wherein 1,3-bis(tert-butylperoxisopropyl)-benzene is the organic polymer-active radical forming agent. 
     
     
       3. The process of claim 1 wherein di-tert-butyl peroxide is the organic polymer-active radical forming agent. 
     
     
       4. A process for the production of shaped bodies and semi-finished products from olefin homopolymers and copolymers crosslinkable by high energy radiation in the presence of a polyfunctional ethylenically unsaturated monomer capable of reducing the radiation dosage for croslinking said olefin polymer comprising: a. forming a mixture of said olefin polymer, monomer and from 0.05 to 0.5% based on the weight of said olefin polymer of at least one organic polymer-active radical forming agent selected from the group consisting of diaryl peroxides, alkaryl peroxides, and dialkyl peroxides;   b. shaping said mixture and heating said mixture during shaping at a temperature above the decomposition temperature of said radical forming agent until said agent decomposes and a shaped crosslinkable body is formed whereby oligomerization of said monomer occurs so as to substantially prevent migration of said monomer to the surface of said shaped body; and   c. crosslinking said shaped body with high energy radiation.   
     
     
       5. The method of claim 4 wherein said diaryl peroxide is dicumyl peroxide. 
     
     
       6. The method of claim 4 wherein said alkaryl peroxide is 1,3-bis (t-butylperoxisopropyl)benzene. 
     
     
       7. The method of claim 4 wherein said dialkyl peroxide is di-tert-butylperoxide. 
     
     
       8. A process for the production of shaped bodies and semi-finished products from olefin homopolymers and copolymers crosslinkable by high energy radiation in the presence of a polyfunctional ethylenically unsaturated monomer selected from the group consisting of di-allyl esters of organic carboxylic acids, allyl ethers, acrylate or methacrylate esters of an alcohol selected from the group consisting of mono di-, tri- and tetra-ethylene glycols and bi- or polyvalent alcohols, allyl cyanurates, N,N-diallyl melamine and dimaleimides comprising: a. forming a mixture of said olefin polymer, monomer and from 0.05 to 0.5% based on the weight of said olefin polymer of at least one organic polymer active radical forming agent selected from the group consisting of dicumyl peroxide, 1,3-bis(tert-butyl peroxisopropyl) benzene and di-t-butylperoxide   b. shaping said mixture and heating said mixture during shaping at a temperature above the decomposition temperature of said radical forming agent until said agent decomposes and a shaped crosslinkable body is formed whereby oligomerization of said monomer occurs so as to substantially prevent migration of said monomer to the surface of said shaped body; and   c. crosslinking said shaped body with high energy radiation.